I. Field of the Invention
The present invention relates to water ski tow handles.
II. Description of the Prior Art
There are a plurality of previously known water ski tow handles comprising a tubular and cylindrical core bar which is covered or encased by a resilient material. For example, U.S. Pat. No. 3,092,068 to Brownson discloses such a water ski tow handle. In addition, in the Brownson patent, a pair of plugs 12 and 12' are positioned within the interior of the core bar and form a flotation chamber 26 therebetween for the water ski tow handle. U.S. Pat. No. 3,537,418 to Brownson also discloses a water ski tow handle having a tubular and cylindrical core bar covered by a resilient material and in which a pair of plugs 24 are positioned within the core bar and form a flotation chamber therebetween.
One disadvantage of these previously known water ski tow handles, however, is that the tow line for the handle is attached only to the core bar itself. Since these core bars are conventionally constructed of a relatively thin wall metal, the strength of the tow handle against bending or breakage is necessarily limited to the strength of the core bar. While these previously known water ski tow handles are sufficient for most purposes, such tow handles are inadequate for high speed or competitive water skiing.
A still further disadvantage of these previously known water ski tow handles is that the resilient covering for the core bar cannot be placed over the core bar under high pressure and high temperature conditions such as exist during an injection molding or transfer molding process. Rather, when these previously known water ski tow handles are subjected to injection molding, the pressures present during the injection molding longitudinally displace the plugs within the core bar and squash these plugs together. Simultaneously,the injected material fills the interior of the core bar up to the plugs so that the water ski tow handle no longer floats.
One method attempted by the Applicant to prevent the displacement of the plugs during injection molding is been to create a relatively large interference fit between the plugs and the interior of the core bar and then to press fit these plugs into the core bar. This attempt, however, has proven unsuccessful. It is believed that during the elevated temperatures present during an injection molding process, the core bar expands beyond its yield point or point of elasticity. Consequently, the core bar fails to completely thermally contract upon cooling so that the fluid seal between the plugs and the core bar is lost. Without this fluid seal, the air within the flotation chamber expels past the plugs during the injection molding process thus forming a vacuum within the core bar. As the core bar cools, the vacuum draws the injected or other material within the flotation chamber thus destroying its effectiveness.
Attempts have also been made by Applicant to fill the interior of the core bar with a light weight material, such as foam, in order to achieve the desired flotation for the tow handle. Such attempts, however, have also proven unsuccessful since the high pressures during the injection molding process merely squash the foam together. The use of more rigid materials, such as a wooden dow to prevent this unduly increases the weight of the overall core bar so that it no longer floats.